Nov 22, 2003

Nov 18, 2003

Starting today Cross·Spectrum is offering a new service:
Microphone Frequency Response Measurements.
The primary purpose of this service is to address the needs of DIY’ers who have
purchased low-cost capsules, and want to know the response of their
individual microphone. I think it will also be useful to organizations
who may want to check the responses of
their precision microphones for diagnostic purposes.

Please take note that we in no way, shape or form claim that service
represents a NIST-traceable calibration. In particular, our
measurement procedure is similar to the
“substitution” method, and there will be some inaccuracy at higher
frequencies where the acoustic wavelengths begin to approach the size of the
microphone diaphragm. Also note that the phase response is determined via Hilbert Transform - the
Hilbert Transform is only valid for minimum phase systems, and unfortunately,
many microphones are not minimum phase devices. However, we believe this service will help
to diagnose problems with microphones at a much lower cost than hiring
a calibration laboratory.

The process is pretty simple - send us your microphone and pre-amp, and
we’ll run it through our test suite which compares the performance of your
microphone with a NIST-calibrated mike. We’ll then send you a
summary report
that documents the measurement results.
We may also be able to give you a calibration file for use with
programs like WinAudioMLS,
provided we can figure out the file format.

Price for the service is $30US, including return shipping (continental US only),
and we accept checks or credit cards via PayPal. We can also make
arrangements for oversease shipping. In most cases we should be able to turn
around your microphone in 24 to 48 hours. Please
contact us
for more details.

Nov 08, 2003

Time to give credit where credit is due:
“Neighbors complain; RTD noise quieted“ —
residents complained about noise from an RTD facility (Denver), and RTD did something
about it. Good job.

RTD’s actions are an example of one of the best-kept secrets in noise control:
a token effort directed at the noisiest activity will often resolve noise complaints.
I’m not talking about spending thousands of dollars for noise barriers or
drastically readjusting schedules. Often, simple things will help reduce
the negative affects of noise, and demonstrate to the community that you are sensitive
to its needs.

For example: I worked as a nighttime “noise cop” on a large construction
project a few years ago. An ongoing construction activity was located near an
apartment building. The construction noise wasn’t particularly loud (it was well
within the noise specifications I was enforcing) but it did generate a constant noise
that was audible inside the building.

For three nights in a row, a woman in the building called the noise hotline at
exactly 11:25pm each night. We did our best to accommodate her, but we were curious as
to why she called at 11:25 each night, especially since the activity she complained
about usually started at around 7:00pm. The we figured it out: we postulated that
the woman came home from work, turned on the television, and kept it on for the night.
The noise from the
television masked the noise from the construction, and she didn’t notice it!
However, she apparently watched the evening news, but turned off the TV after the
weather report, which ended at 11:25. When she turned off her television,
she noticed the construction noise, and she called the hotline because she
feared the noise would prevent her from falling asleep.

The solution was simple. Usually the construction crew took their “lunch”
break at midnight. We had them take their break starting around 11:15pm instead.
When the woman turned off her television, she didn’t hear the construction
activity. The crew started up their work around midnight, presumably when the woman
was asleep. Because the noise level from the work was relatively low, the noise
was not likely to awaken her. We continued with this schedule for 2 weeks, and
had no further complaints.

Again, a simple method that provided an effective solution to the problem at minimal
cost and disruption to the schedule. It doesn’t take a lot of effort
to be the good guy.

The St. Petersburg Times (Florida) is running a profile on the
inventer of surround sound.
When they say he “invented”
surround sound, I assume they are talking about
matrixed surround sound, since
discrete surround sound had been around in several forms prior to 1967
(Fantasia
being one of the prominent early examples).

Diane Carter (another acquaintance from jobs past) is in the news, measuring
airplane sound levels to assist in
land-use planning.

NoiseLaw.org
has set an ambitious goal: “to collect in one place
all existing ordinances in the United States.”
and in Canada relating to noise in its many forms.

Nov 05, 2003

Slashdot
points to this article
from Syllabus magazine, titled
“The FREE, 0% APR, Better Sex, No Effort Diet: Syllabus.” The
article basically asserts that Free Software and
Open Source software are just
forms of “the mythical free lunch.” In other words, stay away from
open source software because you always get what you paid for.

Where to start? Open source and Free software has made a big splash in the
news over the last few years with the emergence of
Linux, but the fact of the matter is that
open source software has been a staple of computing for at least 40 years. The
infrastructure was developed using open source/Free software, and most mail
servers and web servers (including this one) are served using open source server
packages.

So why should you care about open source software? Frankly I don’t know; but I
can tell you why I care about open source software: it gives me
alternatives. Better yet, it allows me to perform my required computing tasks such as
typesetting, numerical processing,
plotting and
GIS
at comparable quality and much lower costs than proprietary
alternatives. Not bad for $0.

I’ve used open source software to build robust data
analysis systems that
have significantly reduced analysis time and provided increased flexibility.
These systems would have cost several thousands of dollars to implement using
proprietary systems, while providing little increase in quality.
This has both increased efficiency for projects I’ve worked on, and saved money
for my clients.

Now I’m not trying to say that open source software is suitable for all tasks; it’s not.
In fact my primary computers run the “non-free”
Mac OS X operating systems and my
data loggers run Windows. But in
choosing these platforms, I considered alternatives like Linux, and
NetBSD and picked what was cost-effective for me.

So if you feel the need to drop big money on proprietary software without
considering the alternatives, go right ahead —
it makes it that much easier
for me to compete.

The New York City council takes note on NYC’s
noise problems.
The article makes specific reference to New Yorks subway system.
It may not be common knowledge, but
New York City Transit
actually does a lot of work to reduce noise and vibration on their system. Noise levels
could be lower, but considering that the system has 650+ miles of track and
several hundred vehicles, NYCT is doing pretty well with limited resources.